The indirect effect of radiation plays an important role in radio-induced biological damages. Monte Carlo codes have been widely used in recent years to study the chemical evolution of particle tracks. However, due to the large computational efforts required, their applicability is typically limited to simulations in pure water targets and to temporal scales up to the µs. In this work, a new extension of TRAX-CHEM is presented, namely TRAX-CHEMxt, able to predict the chemical yields at longer times, with the capability of exploring the homogeneous biochemical stage. Based on the species coordinates produced around one track, the set of reaction–diffusion equations is solved numerically with a computationally light approach based on concentration distributions. In the overlapping time scale (500 ns–1 µs), a very good agreement to standard TRAX-CHEM is found, with deviations below 6% for different beam qualities and oxygenations. Moreover, an improvement in the computational speed by more than three orders of magnitude is achieved. The results of this work are also compared with those from another Monte Carlo-based algorithm and a fully homogeneous code (Kinetiscope). TRAX-CHEMxt will allow for studying the variation in chemical endpoints at longer timescales with the introduction, as the next step, of biomolecules, for more realistic assessments of biological response under different radiation and environmental conditions.

Nanocrystalline (NC) materials have widespread industrial usage. X-ray and neutron diffraction techniques are primary tools for studying the structural and microstructural features of NC materials. Selected area electron diffraction (SAED) patterns collected using a transmission electron microscope (TEM) on polycrystalline nanostructured materials, featuring nested rings, that are analogous to Debye–Scherrer patterns, possess similar potentials to aid materials characterisation. The utility of SAED patterns is further enhanced by the possibility of applying crystallographic approaches, like full pattern fitting procedures, based on Rietveld refinement algorithms, enabling the evaluation of material features, such as crystallite size, lattice distortions, defect structures, and the presence of secondary phases even from very small volume scale. In this paper, we have discussed the possibilities afforded by a Rietveld code applied to SAED patterns of NC materials, including the mathematical implementation of the two-beam dynamical correction model in MAUD software (version 2.9995), and a critical discussion of the results obtained on different NC materials.

Objective . Radiation biophysical modelling of the spatio-temporal events following energy deposition in a tissue-like medium is a useful tool for investigating mechanistic features of radiobiological processes. The present study focuses on the description of complex milieux and long time domains. Approach . Monte Carlo (MC) chemical track structure algorithms allow the formation, transport, and recombination of radical species under various irradiation conditions to be followed. This feature has been proposed to have outermost relevance, e.g. in the comprehension of the FLASH effect. Nevertheless, to extend the simulations predictability range in both temporal scales and realistic environments, while avoiding prohibitive running times, computationally lighter approaches have to be used in combination with the accurate step-by-step descriptions provided by MC. To this end, TRAX-CHEMxt has been implemented. Main results . We propose here an upgraded version of the code, capable now to investigate the chemical effects of radiation up to 1 s and in a more complex environment, featured not only by oxygenated water, but also by a representative biomolecule, RH, and an antioxidant component, XSH. The robustness of the code in this new configuration has been proven. Its predictions are compared with both full MC counterparts at the overlapping time scale, (1–10) µ s, and available experimental data at longer temporal points, showing in all cases good agreements. The change in the chemical yields due to the presence of RH and XSH is then investigated, as a function of primary particle type, energy, LET, and target oxygenation. Significance . TRAX-CHEMxt can thus be effectively applied to study the impact of radiation-induced radicals at larger time scales on more complex systems, allowing for specific biological targets simulations.

In this paper we study the foundations of the algebraic treatment of classical and quantum field theories for Dirac fermions under external backgrounds following the initial contributions made by several collegues. The treatment is restricted to contractible spacetimes of globally hyperbolic nature in dimensions $d\ge 4$. In particular, we construct the classical Møller maps intertwining the configuration spaces of charged and uncharged fermions. In the last part, as a first step towards a quantization of the theory, we explore the combination of the classical Møller maps with Hadamard bidistributions and prove that they are involutive isomorphisms (algebraically and topologically) between suitable (formal) algebras of functionals (observables) over the configuration spaces of charged and uncharged Dirac fields.

In this paper we study the foundations of the algebraic treatment of classical and quantum field theories for Dirac fermions under external backgrounds following the initial contributions already present in various places in the literature. The treatment is restricted to contractible spacetimes of globally hyperbolic nature in dimensions $$d\ge 4$$d ≥ 4 and to external fields modelled with trivial principal bundles. In particular, we construct the classical Møller maps intertwining the configuration spaces of charged and uncharged fermions, and we show some of its properties in the case of a U(1) gauge charge. In the last part, as a first step towards a quantization of the theory, we explore the combination of the classical Møller maps with Hadamard bidistributions and prove that they are involutive isomorphisms (algebraically and topologically) between suitable (formal) algebras of functionals (observables) over the configuration spaces of charged and uncharged Dirac fields.